This is a fall season that asks viewers to swallow the implausible, from alien invaders on the CBS science fiction series “Threshold,” to sea monsters on NBC’s “Surface.”

ABC is stretching credibility to the outer limits with its new White House drama. The vice president of the United States is on an official visit to France, and Parisian school children actually sing “America the Beautiful”?

We think not.

Other than that, however, “Commander in Chief” is not so farfetched. When Republican President Teddy Roosevelt Bridges suffers an aneurysm, White House aides turn to Vice President Mackenzie Allen (Geena Davis), a woman and independent who was put on the ticket to appeal to women’s hearts, not because she was the best choice to be placed a heartbeat away from the presidency.

Hurried out of the cherubic concert and onto Air Force Two, Mackenzie discovers that all the president’s men – and his sour-faced attorney general, Melanie Blackstone (Leslie Hope) – expect her to step aside because she is not a Republican and does not share the president’s conservative agenda. And she almost does resign, until the right-wing speaker of the House, Nathan Templeton (Donald Sutherland), who is next in line to become commander in chief, says something to her about women that is so offensive that she decides she will take the oath of office after all.

“Commander in Chief” is a political fantasy, a feminist twist on “The West Wing,” which this season pits a Hispanic Democratic nominee against a Republican challenger. And like “The West Wing,” the series has a romantic vision of government.

Furthermore:

Mackenzie’s husband, Rod (Kyle Secor), is told he can no longer serve as his wife’s chief of staff, and is banished to the East Wing. He recoils from the dainty, salmon-pink office assigned to the First Gentleman, but his new social secretary, Norah (Kristen Shaw), reminds him that Mrs. Clinton had her office in the West Wing. “That didn’t go over very well,” she says sweetly.

Geena Davis is serenely strong in the part of president. The show’s creator, Rod Lurie, said he modeled the character not on Mrs. Clinton or Elizabeth Dole, but on Susan Lyne, the former president of ABC Entertainment who is now at the helm of Martha Stewart Ominimedia. Mackenzie is commanding – and sometimes sharp-edged. When the stricken president’s chief of staff, Jim Gardner (Harry J. Lennix), tries to assert himself by saying, “I must insist,” she cuts him off with Thatcheresque hauteur. “Jim, you’re not in a position to insist how I take my coffee.” And then she orders him to get the joint chiefs on the phone.

It’s easy to scoff at some of the prosaic license taken by “Commander in Chief,” but the very fact that viewers can quibble with depictions of presidential power or protocol, and not just whether contestants on Fox’s “So You Think You Can Dance” really can, is kind of neat. Crime and medical series demand a leap of faith; most of us are not schooled enough in microbiology or legal procedure to judge just how far series like “House” or “Law & Order” stretch the facts. But most viewers vote, or say they will, and foreign policy is a home game everybody can play.

Ours is a culture where videos like “Girls Gone Wild” inspire campus copycats and even serious dramas like “CSI” inspire students to sign up for forensic-science courses in droves. It would not be so bad if “Commander” prompted some young viewers to study foreign affairs or even just buy a map.

After the president dies, Mackenzie first must contend with Nathan Templeton. Mr. Sutherland brings a deliciously cunning undertone to a speaker of the House who is so out of touch with modern mores and human psychology that he insults the vice president as a woman and as a leader while trying to persuade her to step aside. He assures her that Islamic nations will never accept a woman as leader of the free world. “Not only that, Nathan,” she retorts sarcastically, “but we have the whole once-a-month, ‘will she/won’t she press the button?’ thing.” He laughs nastily and says, “Well, in a couple of years you’re not going to have to worry about that anymore.” By the time he gets around to deriding her decision to intervene and save a Nigerian woman condemned to death for adultery, he has sealed his own, and the nation’s, fate.

Personal antipathies are as important to politics as position papers or ideological alliances. Every election cycle, some senators decide to run for the highest office less from a sense of mission than a deep dislike of the esteemed colleague who claims that destiny calls. (“Why him and not me” is as much a foundation of democracy as divine inspiration.)

“Commander in Chief” offers a lofty vision of public service, but luckily, it is also veined with a more devilish look at the vanity of public servants.